Various systems have been proposed for obtaining or deriving oxygen association rate curves for a blood sample or a hemoglobin solution. These systems fall into two general categories, namely, (1) systems of the optical type, measuring absorbance of a monochromatic beam as a function of oxygenation of the sample, or (2) systems electrically measuring transport of oxygen through a gas-permeable membrane without relying on optical measurements. Typical prior art systems of the optical type employ dual-wavelength spectrometry, involving fairly complex and expensive optical apparatus.
In another typical prior art system (Winslow, R. M. etal, Journal of Biological Chemistry, Vol. 252, No. 7, April 1977, pp. 2331-2337) the source of oxygen is hydrogen peroxide. The H.sub.2 O.sub.2 is pumped into a whole blood sample and is reduced in the presence of catalase to form O.sub.2 and water. An advantage of the H.sub.2 O.sub.2 method is that the percent saturation is more precisely determined than by conventional dual-wavelength spectrometry. However, H.sub.2 O.sub.2 cannot be used with hemoglobin solutions because it is too violent an oxidizing agent. Further, since H.sub.2 O.sub.2 is being added to the whole blood sample, the system must be capable of changing volume with no total pressure change, i.e., must be open to the atomsphere. This causes problems with red blood cell settling and/or O.sub.2 diffusion from the atmosphere. Finally, the prior system does not permit one to investigate the hemoglobin-oxygen dissociation curve, i.e., the system cannot be run in reverse.